According to Ryan Snodgrass's excellent book on the early 3.0L 930s, this was an ECE (UN Economic Commission for Europe) sticker that certified that a particular car met specific regulations for sale in various European countries. Evidently starting w/ 1975 model year all 930s delivered in European countries (Germany, Italy, France, etc) had these. E1 refers to Germany regs, E2 for France, etc.
So I don't think these varied from chassis to chassis, and it sounds like one sticker was used for all of European markets (vs something specific to a country like the AMAG metal tags for Swiss cars), but the numbering may have varied from model year to model year based on which regs were certified. The circles in the sticker evidently are a form of tamper proofing, e.g. if you try to remove the sticker to put it elsewhere it'll be destroyed in the process.
I don't know if they're still available, but if you scroll down this page on his site it shows a repro sticker there.
930 Turbo: Parts, Decals, and Accessories